There are the known flat glass fibers of the flat cross section as glass fibers used in nonwoven glass fiber fabric and others. When nonwoven fabric is made by paper making of the flat glass fibers, the flat glass fibers overlap each other with their longitudinal directions being horizontal, which can increase the bulk density of the nonwoven fabric and which can provide the nonwoven fabric with high strength by binding with a small amount of a binder. For these reasons, attention is recently being given to the technology of forming the nonwoven glass fiber fabric using the flat glass fibers.
In general, the glass fibers are produced by an operation of retaining molten glass in a melting furnace equipped with a bushing and drawing the molten glass out of nozzle holes formed in the bushing. The aforementioned flat glass fibers can be produced by drawing the molten glass out through the nozzle holes of flat shape.